1. Field of the Invention
The present invention relates to antenna devices that are shared by communication systems that use communication signals in mutually different frequency bands and to electronic apparatuses that include such antenna devices.
2. Description of the Related Art
With recent advancements in functionality, antennas not only for voice communication but also for various communication (broadcasting) systems, such as a GPS, a wireless LAN, and terrestrial digital broadcasting, are being embedded in such systems.
Japanese Unexamined Patent Application Publication No. 2007-194995, for example, discloses an antenna device that is shared by communication systems that use communication signals in mutually different frequency bands.
Housings, which used to be made of resin, of small communication terminal apparatuses, such as cellular phone terminals, have their entire surface plated with metal or the like in order to counter a degradation in the mechanical strength associated with the reduction in the size and thickness of the housings, and thus the housings are being “metalized.” However, if an antenna is embedded inside a metalized housing, a signal outputted via the antenna is blocked by the metal, leading to a problem in that communication is not possible. Therefore, typically, a structure in which part of a housing is formed of nonmetal, and an antenna is mounted in the vicinity of the nonmetal portion is employed.
Recently, however, a case in which an HF band RFID system, such as NFC (Near Field Communication), is embedded has been increasing. If an antenna coil used in this HF band RFID system is to be disposed in the nonmetal portion as well, it becomes very difficult to secure a space necessary for the antenna.
In other words, how to form and integrate an antenna applied in a plurality of frequency bands has been an issue.
The aforementioned situation is applicable not only to an antenna for communication or broadcast reception but also to an electronic apparatus that includes an antenna for electric power transmission (electric power transmission/reception unit) in a similar manner.